1. Field of the Invention
The invention relates to a coupling device with a centrifugal mass facing a drive train.
2. Discussion of the Prior Art
German reference DE 41 22 135 A1 describes (e.g., in FIG. 1) a coupling device in the form of a hydrodynamic torque converter, in which a centrifugal mass that faces the drive train consists of a radial flange. The radial flange runs radially outward from a bearing journal mounted via a holding means in the gear housing and is securely connected to the pump shell of the pump wheel. On the other hand, the turbine wheel forms, with an output shaft, an output-side centrifugal mass.
The radially inner bearing journal is embodied with an internal tooth system, which engages into an external tooth system on a drive shaft. The drive shaft also has an external tooth system at its other end, via which it engages into a corresponding internal tooth system on the crank shaft of an internal combustion engine. The drive shaft thus serves as a driving gear for the centrifugal mass facing the drive train.
Although a rotation-proof connection between the drive train and the centrifugal mass is thus established by the drive shaft, it is unavoidable, due to play in the tooth systems, that when torsional vibrations occur, there is rattling in the area of these tooth systems.
It is also problematic in this known coupling device that neither the holding means for the bearing journal nor the drive shaft ensures the axial attachment of the centrifugal mass that faces the drive trainxe2x80x94and thus of the entire torque converterxe2x80x94to the crank shaft. As a result, the torque converter can carry out axial movements, which must be supported in the gearbox and could lead to damage there.
To avoid these problems, a plate that is elastic in the axial direction is usually screwed to the free end of the crank shaft of the drive train, as shown in FIG. 1 of German reference DE 32 22 119 C1. The plate, in the radially outer area, is also screwed to the drive-side centrifugal mass of the coupling device, which, in this case, is again a hydrodynamic torque converter. However, this solution is expensive, because the screw connection of the flexible plate to the centrifugal mass requires that threaded blocks, which serve to hold the screws, be distributed around and attached to the circumference at a certain distance from each other. Moreover, a screw connection of the flexible plate to the centrifugal mass of the coupling device is highly problematic due to cramped space conditions and difficult access.
The object of the present invention is to provide a coupling device that can be attached to a drive train without play in the circumferential direction, and that has the least possible assembly expense.
Pursuant to this object, and others which will become apparent hereafter, one aspect of the present invention resides in a coupling device which has a driving gear that acts on a drive train and has a centrifugal mass facing the drive train which is in rotation-proof active connection with the driving gear. In accommodating fixture is provided on the centrifugal mass so as to face the driving gear. The accommodating fixture having a first toothed system. The driving gear has an axial shoulder embodied with a second tooth system on a side facing the accommodating fixture so that at least one tooth of the second tooth system engages into a space between two teeth of the first tooth system whereby the teeth of at least one of the two toothed systems are under radial prestress relative to the other toothed system.
Because the driving gear, which is attached to the drive train, e.g., the crank shaft, of an internal combustion engine, has an axial shoulder, on which is embodied at least one tooth of a tooth system that engages into a corresponding tooth system on an accommodating fixture attached to the centrifugal mass, a rotation-proof connection can be established between the accommodating fixture and the driving gear, and thus between the drive train and the centrifugal mass. Since at least one of the two tooth systems is under radial prestress relative to the other tooth system, the connection between the driving gear and the accommodating fixture is substantially without radial play. For example, when there is radial prestress of the tooth or teeth embodied on the axial shoulder of the driving gear, these teeth are pressed as deeply as possible into the tooth system of the accommodating fixture, so that a force-locking connection to the tooth system of the accommodating fixture is established. This works especially well when the tooth faces of both tooth systems are embodied with wedge-like surfaces, so that a tooth of the driving gear tooth system penetrates radially between two teeth of the tooth system of the accommodating fixture, for example, and is clamped at a predetermined penetration depth. When connected to each other in this fashion, the tooth systems of the driving gear and the accommodating fixture have no play between them, so that even during strong torsional vibrations no rattling can occur. In addition, due to the aforementioned clamping of the teeth of the driving gear in the tooth system of the accommodating fixture, an advantage results during the transmission of torque, namely, due to the torque, a circumferential force acts on the teeth. Because the teeth are engaged with each other without play, each tooth is supported in the circumferential direction, so that the tooth base is not loaded with a bending moment. Instead, each tooth needs only to be supported against transverse forces, so that the load remains limited. This advantage is especially important when the teeth of the driving gear tooth system are supportable by the teeth of an accommodating fixture that is embodied as a ring, for example, and thus has a tooth system whose form is stable in the circumferential direction. The advantage is especially great when the ring-shaped accommodating fixture surrounds the driving gear and is equipped with an internal tooth system, so that the radial prestress of the tooth system of the driving gear, upon rotation, is supplemented by centrifugal force, while the ring surrounding the tooth base of the tooth system on the accommodating fixture radially supports the teeth of the tooth system on the driving gear.
According to another embodiment of the invention, the driving gear tooth system has an axial protection means embodied, for example, as a claw with a radial holding device that engages into a radial depression on the accommodating fixture. When the radial holding device is embodied in wedge-like fashion, a clamping connection is again established with the matching radial depression in the accommodating fixture.
As noted above, the driving gear tooth system is radially prestressed relative to the accommodating fixture. To establish an engaged connection between the driving gear and the accommodating fixture when the accommodating fixture is moved onto the driving gear, an assembly mechanism is used. The assembly mechanism acts on the driving gear so that the axial shoulder of the driving gear is deformed against the prestress effect, so that the engaged connection between the driving gear and the accommodating fixture is established substantially without axial force. As soon as this connection is established, the activity of the assembly mechanism is terminated. This can be done either by removing the assembly mechanism completely from the driving gear or, if the assembly mechanism is to remain on the driving gear, by detaching the assembly mechanism so that it can no longer exert any influence on the driving gear tooth system.
Because the axial shoulder on an axially free end of the driving gear serves as the support surface for the assembly mechanism, the assembly mechanism needs to apply only a relatively small assembly force in the radial direction. This is due to the lever effect of the axially free end relative to the other end, which is attached to the radial flange of the driving gear. The assembly force can thereby be smaller than the prestress force that acts in the direction of the tooth system of the accommodating fixture. This advantageous ratio of assembly force to prestress force allows such a high prestress force to be selected that the friction force in the tooth system alone suffices to block axial movement between the driving gear and the accommodating fixture. As a result, no additional axial securing means is needed.
However, if an axial securing means for the connection between the driving gear and the accommodating fixture is attached to the aforementioned free end of the axial shoulder, this axial securing means can engage into the accommodating fixture in the axial extension area of the tooth system. This results in a very low axial space requirement.
According to a further embodiment, the radial flange of the driving gear can be embodied with an axially elastic flange. The axial elasticity can be increased by embodying the latter flange with an elastic spring coil, so that wobbling movements of the crank shaft can be better compensated for. Advantageously, such an elastic spring coil on the flange is even more effective when equipped with a damping means, consisting preferably of an elastomer, which fills, at least partially, the radial empty space created by the spring coil. A damping means of this type can damp vibrations on the spring coils triggered by the aforementioned tumbling movements of the crank shaft.
Following the example of the driving gear, the accommodating fixture can also be embodied with an axially elastic flange. This measure can introduce additional axial elasticity into the connection between the converter housing and the crank shaft, especially when the axially elastic flange of the accommodating fixture has an elastic spring coil. In addition, when the axial shoulder of the accommodating fixture is embodied at its free end with a receiving surface for an assembly mechanism, a high radial prestress force can be attained between the tooth systems of the driving gear and the accommodating fixture at tolerable assembly forces. As explained above, a rattle-free connection can thus be attained between the tooth systems and, at the same time, additional axial securing means can be dispensed with.
To obtain the coupling strength required in coupling arrangements of this type, the interengaged and reciprocally prestressed tooth systems must rest on each other with relatively great radial prestress and/or the components used must be suitably rigid. However, this means that, to establish or detach the coupled state, relatively great radial force must be exercised on at least one of the tooth systems. The present invention therefore proposes, according to a further embodiment, an assembly mechanism that is able to produce the radial forces required in such couplings. In particular, the invention proposes an assembly mechanism that can establish or detach a toothed engagement between the tooth systems of two components, which tooth systems engage with each other at least radially, and wherein the radially inner tooth system is prestressed radially outward toward the radially outer tooth system, while the component with the radially inner tooth system is radially deformable elastically at least in the area of its tooth system. The assembly mechanism comprises at least one ring element, which is or can be rotatably attached to the component that has the radially inner tooth system. The ring element(s) has a deformation formation via which, upon rotation of the ring element around a rotational axis, the radial position of the component with the radially inner tooth system can be changed in the area of the radially inner tooth system.
This assembly mechanism is preferably constructed so that the deformation formation has, associated with each tooth or group of teeth of the radially inner tooth system, a deformation bevel that extends in the circumferential direction. This deformation bevel is directed radially inward and has, in the circumferential direction, a varying distance to the rotational axis. The deformation bevel allows a rotational movement to be simply converted into a radial movement; specifically, the conversion ratio, and thus the rotary force to be expended, can be determined by the inclination angle of the deformation bevel or bevels.
For example, it is possible for an area of minimum distance between the deformation bevel and the rotational axis and/or an area of maximum distance between the deformation bevel and the rotational axis to be followed in the circumferential direction by an area with approximately constant spacing from the rotational axis. Approximately constant spacing can also load a short area extending substantially tangentially to a radial line.
Preferably, the assembly mechanism according to the invention has two ring elements.
These two ring elements encompass deformation bevels running in opposite directions. Each tooth or group of teeth has associated with it a bevel pair, consisting of a deformation bevel from each ring element.
With such an assembly mechanism, the procedure for establishing or detaching the coupling engagement can be one in which the two ring elements are rotated or rotatable around the rotational axis in opposite directions.
It is thereby advantageous for the two ring elements to be prestressed relative to each other for rotation in the circumferential direction, preferably into a relative rotational position in which the coupling engagement is established between the tooth systems.
To establish or detach the coupled state by means of the assembly mechanism according to the invention, in another embodiment ring element(s) have a tool activity formation to be acted upon by a tool, via which the ring element can be rotated around the rotational axis.
To ensure that the assembly mechanism according to the invention is constructed very simply, i.e., economically and with low total weight, the ring element(s) are held rotatably on the component that has the radially inner tooth system. That is, the ring element is to remain permanently on this particular component, even when the coupled state is established.
The present invention also relates to a coupling device for establishing a rotary coupling between two component groups rotatable around a rotational axis. The coupling device comprises a first element with a first tooth system, associated with one of the component groups, and a second element with a second tooth system, associated with the other component group. The two tooth systems engage radially with each other and are prestressed radially into engagement. Such a coupling device can advantageously be equipped with an assembly mechanism as discussed above.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.